1. Field of the Invention
The present invention relates to content management technology for collectively managing a plurality of contents in a device configuration that is connected by a network.
2. Description of the Related Art
In recent years, in addition to personal computers (PCs) and dedicated storage devices, devices equipped with a function that stores content data (hereunder, referred to simply as “content”) have become widely available. Examples of this kind of device include a camera that has a function that stores captured image content or a disk recorder that stores broadcast content and the like. Further, accompanying the widespread use of networks, environments in which devices such as those described above are connected by a network are also becoming common. In this kind of environment, sharing of data processing functions and mutual sending and receiving of content is enabled by communication between a plurality of devices, thereby enhancing the convenience of the devices.
A standard communications protocol called “universal plug and play (UPnP)” is becoming widely used in such cases to realize operations and notification of abilities between the plurality of devices. Further, standard communications protocols such as digital living network alliance (DLNA) that is an extension of universal plug and play (UPnP) are also in widespread use. For these kinds of communications protocols, a system called “content directory service (CDS)” exists that manages the stored content and sends the information thereof to the outside.
In a configuration that utilizes a communications protocol as described above, an apparatus that has a storage function operates as a content server that provides content stored inside the apparatus. The content stored in the content server can be utilized from an arbitrary operation terminal without depending on the apparatus or OS. That is, the content server manages a list of the stored content (content list), and discloses this list to the operation terminal to make it possible to refer to the content managed in the server from the outside. Further, the operation terminal can perform an operation to, for example, display, playback, edit, duplicate, move, or search the content stored inside each content server.
When performing an operation with respect to the content as described above, in most cases the operation terminal utilizes metadata in accordance with the above described communications protocol that is appended to the content. Therefore, when moving the content or the like, it is always necessary to append metadata to the content. Each content server issues an identifier (hereunder, ID) in accordance with the above described communications protocol for the stored content, and assigns this ID to the aforementioned metadata to carry out management of the metadata. It is also possible to refer to this metadata from the content list that each content server makes publicly available.
However, in the content (and metadata) management forms as described above, when content is moved between content servers the ID of the content is changed even though the content remains the same. This is because each content server uniquely assigns an ID that is unique to the content server in question to the stored content. When the ID of the content is changed in this manner, it is sometimes not possible to retrieve the desired object in a search operation from an operation apparatus.
To solve the above-described problem, systems have been proposed that manage content by embedding a unique ID (hereunder, referred to as “GUID” (Global Unique ID)) in metadata inside the system. For example, Japanese Patent Laid-Open No. 2004-234158 proposes a system that collectively manages content by each content server adding and embedding a GUID in a unique region of metadata, and then maintaining that GUID even when the content is moved. Further, Japanese Patent Laid-Open No. 2005-063144 proposes a system in which an attribute assigning apparatus assigns a GUID when a user requests the attribute assigning apparatus to register content using a dedicated operation terminal. Furthermore, Japanese Patent Laid-Open No. 9-223130 proposes a data management system in which, with regard to assignment of a GUID, when a dedicated operation apparatus notifies a dedicated management apparatus of the details of an operation with respect to content, the dedicated management apparatus assigns a GUID in accordance with the notified operation.
However, there are the following problems in the above described prior art.
(1) In a case of following the aforementioned communications protocol, when performing an operation such as duplication or movement of content between arbitrary content servers from an arbitrary operation apparatus, there is no means that notifies the content for which the operation was performed or the operation details to the other content server. Therefore, even when an apparatus other than the content server that performed the operation attempts to uniquely manage all the content in the system, the apparatus cannot recognize the details of the operation. Therefore, the apparatus cannot uniquely assign a GUID in accordance with the operation details.
(2) When assigning a GUID only to content inside the own device, as in Japanese Patent Laid-Open No. 2004-234158, it is not possible to manage content within a content server that does not have the ability to assign an arbitrary GUID.
(3) Since the handling of a GUID is the same when content is copied and when content is moved, in the case of performing a search, different content is duplicated and retrieved, and thus the uniqueness of content cannot be preserved.
(4) When performing an operation in accordance with the above described communications protocol, unless the management terminal holds the metadata of all the content and searches all the content in the system each time an operation is performed, the management terminal cannot recognize for which content an operation was performed.